This invention relates to a bone substitute product, such as a material, a sheet, and a method of manufacturing the same. In particular, the bone substitute product is useful in dental, orthopedic, and plastic surgery fields as a filling or cushioning material for root canal filling, bone filling, a tooth support in pyorrhea alveolaris, and so on.
A bone substitute material of the type described is known which comprises a hardenable composition containing chitosan. The chitosan is well-known in the art as a natural abundant macromolecule. Such a hardenable composition is disclosed in Japanese Patent Prepublication No. 22026/1977. In order to manufacture the hardenable composition, an acidic aqueous solution of chitosan should be mingled or mixed with a basic water-hardenable inorganic material because the chitosan itself has a low solubility under a basic state or a non-acid state. As the basic water-hardenable inorganic material, use has generally been made of lime, Portland cement, alumina cement, or the like. The resultant composition is not lower than 9 in the pH value.
However, the above-mentioned conventional hardenable composition is improper for use in a human body because of such a high pH value.
Another conventional hardenable composition is disclosed in Japanese Patent Prepublication No. 208347/1989. The hardenable composition is manufactured by a mixture of an acidic aqueous solution of chitosan, particulate hydroxyapatite, zinc oxide and/or magnesium oxide. Due to presence of such hydroxyapatite, the hardenable composition exhibits an excellent affinity to a tooth and a bone and is hardened within a neutral range.
However, a very long time is required to create a bone when this hardenable composition is used as a bone substitute material.
In a dental field, dental cements have been extensively used for cementation of a restorative material, a temporary filling material, a root canal filling material, and so on. For example, as the dental cements, known are zinc phosphate cement, zinc oxide eugenol cement, and carboxylate cement. Such dental cements are prepared by mingling powder components and liquid components immediately before application and then hardened after lapse of 4 to 10 minutes.
However, such a dental cement has a pH value between 2 and 4 when a mixture of the powder component and the liquid component is prepared in the form of paste. In other words, the dental cement is acidic. When the dental cement is used in a human body for cementation, as mentioned above, dental pulp may be injured (inflammation, stimulation, and so on).
Consideration may be made as regards using the particulate apatite as a bone filling material. However, the particulate apatite often causes inflammation to occur in a gingiva. Specifically, the particulate apatite often migrates from an initial implant site and enters between a bone and the gingiva. This brings about inflammation in the gingiva under an occlusal pressure.
In addition, the hardenable composition containing the particulate apatite is not effective in creation of a bone because the particulate apatite is often migrated to be lost from the implant site.